On February 12th, sunspot AR2699, which had recently morphed into four individual spots, exploded, producing a C1-class solar flare in addition to hurling a coronal mass ejection almost exactly in the direction of Earth.
The sunspots' rapid change in appearance was a significant clue that its magnetic field was changing, a process that can lead to solar flares when the magnetic field twists, turns, and magnetically reconnects to restore equilibrium.
Coronal mass ejection models at NASA and NOAA currently disagree with the timing for when the solar material will impact Earth; the coronal mass ejection could arrive as early as late on February 14th, but is more likely on February 15th.
The coronal mass ejection may be strengthened by a stream of fast moving solar wind particles that was already en route to Earth when the sunspot exploded; if the CME sweeps up material from the stream, much like a snowplow, it may increase the potency of the solar storm when it strikes Earth's magnetic field.
A G1 (minor) geomagentic storm watch is in effect for February 15th. Arctic sky watchers should be alert for auroras when the CME arrives; if the storm intensifies to class G2, observers in Canada and northern U.S. states may have a chance to see auroras as well.
© 2018 Meteorologist Chris Stubenrauch